Communication network and communication node of a communication network

ABSTRACT

The communication network includes a set of links each supporting a specified bandwidth, a set of subscribers and at least one communication node comprising a set of communication ports configured for being connected to links of the network. Each of the subscribers is associated with an authorized maximum bandwidth for transmission on the network, the total of authorized maximum bandwidths corresponding to respective subscriber being less than or equal to the authorized maximum bandwidth associated with respective subscriber. The communication node includes a processing unit configured for, when a data frame is received on one of the communication ports: checking if a memory contains an identifier associated with that data frame; and if the memory does not contain the identifier associated with that data frame: sending that data frame to all of the other communication ports of the communication node and storing the identifier associated with the data frame in the memory.

RELATED APPLICATION

The present application claims priority to French Patent ApplicationNumber 15 52568, filed Mar. 26, 2015, the disclosure of which isentirely incorporated by reference.

TECHNICAL FIELD

The technology herein relates to the field of communication networks andmore particularly to communication networks installed in aircraft.

BACKGROUND

Aircraft generally comprise one or more onboard communication networksprovided to allow communications between onboard equipment, for exampleonboard computers. In order to meet the regulatory requirementsregarding certification of aircraft, an onboard communication networkmust allow a deterministic transmission of data between the differentequipment subscribed to this communication network. The ARINC 664 part 7standard defines a deterministic onboard avionic communication network,based on a full-duplex Ethernet technology. Such a network can forexample correspond to an AFDX® communication network. In a networkconforming with the ARINC 664 part 7 standard, each item of equipment isconnected to a switch of the network and the communications between thedifferent equipment use virtual links predefined during the design ofthe network. A virtual link is defined between an item of transmittingequipment and one or more items of receiving equipment, via one or moreswitches of the network. Each virtual link uses a determined path in thenetwork. A bandwidth is allocated to each virtual link and the routingof the different virtual links of the network is carried out in such away that the total of the bandwidths allocated to the virtual linksusing a same physical link does not exceed the bandwidth supported bysaid physical link. This makes it possible to guarantee the determinismof the network. However, a few constraints result from this, inparticular with regard to the configuration management of the network.All of the communications between equipment must be defined in advance,by the definition of the virtual links, in order to allow aconfiguration of the switches. All communications between the equipmenttherefore must be defined very early in the process of development ofthe systems installed in the aircraft. As a result, the configuration ofthe switches of the network and the configuration of each switch must bedownloaded into respective switch before it is used. This configurationmust be consistent with the subscribed equipment actually connected tothe network. Moreover, when a physical link or a switch of the networkis unavailable, the different virtual links passing through thatphysical link or that switch are unavailable.

SUMMARY OF THE INVENTION

The technology herein seeks to provide a solution to theabove-identified problems. It relates to a communication networkcomprising:

a set of links each supporting a specified bandwidth;

a set of subscribers; and

at least one communication node comprising a set of communication ports,these communication ports being connected to links of the set of links.

This network is noteworthy in that:

each one of the set of subscribers is associated with an authorizedmaximum bandwidth for transmission on the network, in such a way thatthe total of the authorized maximum bandwidths corresponding torespective subscriber is less than or equal to said authorized maximumbandwidth associated with respective subscriber,

said at least one communication node comprises a processing unit and amemory and the processing unit is configured for, when a data frame isreceived on one of the communication ports of the communication node:

checking if the memory contains an identifier associated with that dataframe; and

if the memory does not contain an identifier associated with that dataframe:

sending that data frame to all of the other communication ports of thecommunication node; and

storing the identifier of the data frame in the memory.

Thus, said at least one communication node distributes the received dataframe to all of the other ports. This makes it possible to distributethe frame to all of the destination subscribers, without a configurationof the communication node or nodes of the network. Moreover, by virtueof the identifier associated with a data frame, if the communicationnode in question receives a data frame several times because of thedistribution of said data frame in the network by several communicationnodes, the communication node does not retransmit the data frame. Thismakes it possible to avoid saturation of the communication network byguaranteeing that a same data frame, to which a specified identifiercorresponds, can only be transmitted once by a communication port of acommunication node. Moreover, given that the total of the authorizedmaximum bandwidths associated with each of the subscribers is less thanor equal to the specified bandwidth supported by each of the links, thedata traffic corresponding to data frames transmitted by the differentsubscribers does not risk saturating the communication network. Thecommunication network therefore makes it possible to route a data frametransmitted by a subscriber, to the destination subscriber (orsubscribers), without risking saturation of the network. Moreover, thisnetwork does not necessitate a configuration of virtual links incommunication nodes of the network, which makes it possible tofacilitate modifications of the subscribers of the network. For example,it is possible to modify easily the list of the destination subscribersof a data frame transmitted by a subscriber: such a modification onlynecessitates a parameterization of the transmitting subscriber and/or ofthe destination subscriber or subscribers.

Advantageously, the links of the set of links are arranged in pairs inorder to form a network of the full-duplex type.

According to one example embodiment, the subscribers of the set ofsubscribers are configured for communicating on the network according toa communication protocol compatible with the ARINC 664 part 7 standard.Advantageously, the identifier associated with a data frame correspondsto a virtual link identifier and a sequence number of the frame.

According to another example embodiment, the set of subscribers areconfigured for communicating on the network according to a communicationprotocol compatible with the Ethernet standard. Advantageously, theidentifier associated with a data frame corresponds to an identifier ofthe transmitting subscriber and a frame number generated by thatsubscriber.

In a particular example embodiment, the communication network comprisesat least four communication nodes, each communication node comprisingfour communication ports, these communication nodes being arrangedaccording to a matrix topology.

Advantageously, said at least one communication node is integrated inone of the set of subscribers. This makes it possible to simplify thecommunication network, as the communication network does not needspecific equipment for implementing the functions of a communicationnode. The communication network thus comprises only subscribers and aset of links between these subscribers.

The technology herein also relates to a communication node of acommunication network, this network comprising a set of links eachsupporting a specified bandwidth, the network further comprising a setof subscribers, with each of which is associated an authorized maximumbandwidth for transmission on the network, in such a way that the totalof authorized maximum bandwidths corresponding to respective subscriberis less than or equal to the authorized maximum bandwidth associatedwith respective subscriber, the communication node comprising a set ofcommunication ports, these communication ports being provided for beingconnected to links of the network.

The communication node comprises a processing unit and a memory and theprocessing unit is configured for, when receiving a data frame on one ofthe communication ports of the communication node:

checking if the memory contains an identifier associated with that dataframe;

if the memory does not contain an identifier associated with that dataframe:

sending that data frame to all of the other communication ports of thecommunication node; and

storing, in the memory, the identifier associated with the data frame.

Advantageously, the communication node comprises a transmission queueassociated with a communication port. Such a queue makes it possible tostore data frames received by the communication node, before they areretransmitted, in order to avoid data collisions on the communicationlinks.

The communication node further comprises:

a reception queue associated with a communication port; and

a traffic regulator configured for reading data in the reception queueand for sending these data to the processing unit, whilst limiting thereading and sending of the data in terms of an authorized maximumbandwidth for that communication port.

When this communication port is connected to a subscriber, this makes itpossible to limit the data traffic coming from the subscriber andretransmitted by the communication node on the network, in order toprotect against saturation of the communication network. The authorizedmaximum bandwidth for this communication port is then advantageouslychosen to be equal to the authorized maximum bandwidth for transmissionon the network associated with that subscriber.

The technology herein also relates to an aircraft comprising acommunication network such as mentioned above.

BRIEF DESCRIPTION OF THE DRAWINGS

These and further aspects of the exemplary implementations will bebetter understood on reading the following description and onexamination of the appended figures.

FIG. 1 is a simplified illustration of an example aircraft comprising acommunication network.

FIG. 2 shows a communication network according to one non-limitingexemplary embodiment of the invention.

FIGS. 3, 4 and 5 illustrate non-limiting exemplary communication nodesof a communication network.

FIG. 6 illustrates a non-limiting exemplary subscriber of acommunication network integrating a communication node.

FIG. 7 shows a non-limiting exemplary communication network comprisingsubscribers such as the one shown in FIG. 6.

DETAILED DESCRIPTION

The communication network 20 shown in FIG. 2 comprises a set ofsubscribers 12 a, 12 b, . . . 12 k, 12 l, a set of communication nodes10 a, 10 b, . . . 10 i and a set of communication links 14. In anexample embodiment, the communication network can correspond to acommunication network of an aircraft 1, comprising a cockpit 3, as shownin FIG. 1. In the example embodiment, subscribers of the set ofsubscribers may correspond to computers of the aircraft, for exampleavionic computers. These computers, as well as the communication nodesand the communication links can be situated in an avionics bay 2 of theaircraft.

Each subscriber comprises a communication port connected, by acommunication link 14, to a communication port of one of thecommunication nodes. Each communication node comprises severalcommunication ports, for example 4 communication ports as shown in FIG.2. Communication ports not connected to a subscriber are connected toports of other communication nodes by other links 14. The differentcommunication ports are transmitting and receiving ports and the links14 are arranged in pairs in order to form a full-duplex communicationnetwork. Each link 14 supports a specified bandwidth, for example 100Mbits/s. Moreover, each one of the set of subscribers is associated withan authorized maximum bandwidth for transmission on the network, suchthat the total of the authorized maximum bandwidths corresponding torespective subscribers is less than or equal to the authorized maximumbandwidth associated with respective subscriber. In particular, thebandwidth can be distributed in a similar manner among the differentsubscribers. Thus, an authorized maximum bandwidth of 8.33 Mbits/s canbe associated with each of the 12 subscribers 12 a, 12 b, . . . 12 l.The total of the authorized maximum bandwidths associated with each ofthe subscribers is then equal to the specified bandwidth, for example100 Mbits/s. Alternatively, different authorized maximum bandwidths canbe associated with different subscribers. For example, the 4 subscribers12 a, 12 b, 12 c and 12 d can each have an authorized maximum bandwidthof 10 Mbits/s, the other 8 subscribers each having an authorized maximumbandwidth of 7.5 Mbits/s. The total of the authorized maximum bandwidthsassociated with each of the subscribers is then equal to the specifiedbandwidth, for example 100 Mbits/s. Such a configuration of theauthorized maximum bandwidths for each of the subscribers makes itpossible to guarantee that, even if all of the subscribers aresimultaneously transmitting data on the communication network, all ofthe data likely to pass through a link does not exceed the bandwidthsupported by that link.

As shown in FIGS. 3 and 4, a non-limiting exemplary communication node10 of a communication network comprises, for example, four communicationports P1, P2, P3 and P4. FIG. 3 corresponds to a simplifiedrepresentation of the communication node allowing a better understandingof its operation during the reception of data on the communication portP1: only the elements of the communication node used during saidreception are shown. The communication node 10 comprises a processingunit 16, for example a processor, connected to a memory M. It alsocomprises transmission queues Fe1, Fe2, Fe3 and Fe4 respectivelyassociated with the communication ports P1, P2, P3 and P4. Thesetransmission queues are connected to the processing unit 16 respectivelyby links 18 a, 18 b, 18 c and 18 d respectively. The communication nodealso comprises links 15 a, 15 b, 15 c and 15 d respectively from thecommunication ports P1, P2, P3 and P4 to the processing unit 16,allowing the transmission to the processing unit of data received by thecommunication ports.

During operation, the data flowing on the different links 14 of thecommunication network 20 correspond to data frames. A data frame istransmitted, by a subscriber of the network, to one or to several othersubscribers of the network. When a communication node 10 receives a dataframe on a communication port, for example the port P1, this porttransmits the data corresponding to the received data frame to theprocessing unit 16 by means of the link 15 a. The processing unitanalyzes the data received and retrieves an identifier associated withthe data frame. The processing unit then checks if this identifier isalready recorded in the memory M. If the memory does not contain thisidentifier, then the processing unit sends the data corresponding to thereceived data frame to the queues Fe2, Fe3 and Fe4 associated with theother communication ports P2, P3 and P4, respectively by the links 18 b,18 c and 18 d. The data frame is then retransmitted by each of the othercommunication ports P2, P3 and P4. Moreover, the processing unit 16records, in the memory M, the identifier associated with the data frame.Thus, the communication node 10 retransmits the received data frame onlyif the identifier associated with that data frame was not already storedin its memory M, namely, if the data frame had not yet been received bythat communication node. On the other hand, if the data frame hasalready been received by the communication node, then its identifier isalready recorded in the memory M and consequently the processing unit 16does not send the data corresponding to this data frame to thetransmission queues Fe2, Fe3 and Fe4. Thus, the data frame is notretransmitted by communication ports P1, P2 or P3. This makes itpossible to avoid sending a same data frame several times on a same linkof the communication network, which prevents the saturation of thebandwidth supported by said link. The use of a transmission queueassociated with each communication port makes it possible to avoid datacollisions during transmission, for example, when the communication nodereceives data frames simultaneously on several communication ports, thedata corresponding to these data frames are sent to the transmissionqueues by the processing unit 16. The data is then transmitted by thecorresponding communication ports according to a FIFO (First In, FirstOut) principle.

Each communication node of the communication network retransmits thedata frames received, by each of the communication ports of said node,on all of its other communication ports. This makes it possible todistribute, in the communication network, a data frame transmitted by asubscriber. In particular, in the case of a non-limiting exemplarycommunication network 20, such as the one shown in FIG. 2, of whichcommunication nodes 10 a, 10 b, . . . 10 i are arranged according to amatrix topology, a data frame transmitted by one of the subscribers 12a, 12 b, . . . 12 l is distributed on all of the links 14 of thenetwork, which allows the reception of said frame by all of the othersubscribers of the network. Thus, each subscriber of the network cancommunicate with all of the other subscribers of the network. “Matrixtopology” in this case refers to the fact that the communication nodes10 a, 10 b, . . . 10 i are arranged in rows and columns, for example, 3rows and 3 columns as shown in FIG. 2, each communication node having 4communication ports connected to communication ports of othercommunication nodes or to communication ports of subscribers of thenetwork. The invention is not however limited to such a topology or tocommunication nodes having 4 communication ports and other networktopologies can be envisaged.

In a particular example embodiment, subscribers of the set ofsubscribers are configured for communicating on the network according toa communication protocol compatible with the ARINC 664 part 7 standard.As already indicated, this standard provides virtual links for theexchanges of data frames between the subscribers of the communicationnetwork: a subscriber transmits data frames on a virtual link to one ormore receiving subscribers and each virtual link is allocated with amaximum bandwidth. A virtual link uses physical links of thecommunication network and passes through one or more communicationnodes. Several virtual links can use a same physical link as long as thetotal of the maximum bandwidths allocated to these virtual links doesnot exceed the bandwidth supported by that physical link. In aparticular example embodiment, the authorized maximum bandwidth fortransmission on the network associated with a subscriber of the networkcorresponds to the total of the maximum bandwidths allocated to thedefined virtual transmission links for that subscriber. Consequently,the condition according to which the total of the authorized maximumbandwidths corresponding to each of the subscribers is less than orequal to said specified bandwidth, for example 100 Mbits/s, isequivalent to a condition according to which the total of the maximumbandwidths allocated to each of the virtual links defined in the networkis less than said specified bandwidth. During the design of such anetwork, it is therefore appropriate to define the different virtuallinks in compliance with this condition and the different subscribers ofthe communication network must be configured consequently. In order todo this, the subscribers conventionally comprise virtual linkconfiguration tables. Once the subscribers are thus configured, noconfiguration of the communication nodes is necessary. This makes itpossible to simplify the design the evolution of the communicationnetwork in comparison with the networks of the prior art compatible withthe ARINC 664 part 7 standard, since it is not necessary to configurepaths of the virtual links in switches of the network. Unlike thenetworks of the prior art, when a subscriber of the network transmits adata frame on a virtual link, that data frame is distributed on all ofthe physical links 14 of the network. That frame is therefore receivedby all of the other subscribers of the network. The other subscribersuse their configuration tables to determine whether to accept thereceived frame, for example, only the receiving subscribers of thevirtual link in question accept the reception of the data frame. Giventhat each data frame is distributed on all of the physical links of thenetwork, the network is robust when there is a failure of some of thephysical links. In this particular example embodiment, the identifierassociated with a data frame can for example correspond to thecombination of a virtual link identifier and a sequence number of theframe.

In another example embodiment, the communication network is of thefull-duplex Ethernet type. The identifier associated with a data framecan for example correspond to the combination of the source Ethernetaddress corresponding to the subscriber having transmitted that dataframe with a frame number generated by that subscriber, this framenumber being for example contained in an IP (Internet Protocol) headerfield of the frame.

In an example embodiment shown in FIG. 5, the communication node 10comprises a reception queue associated with at least one of thecommunication ports, in this case a reception queue Fr1 associated withthe communication port P1 and connected to the latter by a link 25. Thecommunication node also comprises a traffic regulator 28 connected onthe one hand to that reception queue and on the other hand to theprocessing unit 16. This traffic regulator can correspond to a softwareapplication used by the processing unit 16 or to a separate processingunit. Alternatively, the traffic regulator can be implemented in ahardware manner by an electronic circuit in the communication node. Thetraffic regulator is configured for reading data in the reception queueand for sending these data to the processing unit, whilst limiting thereading and sending of the data in terms of an authorized maximumbandwidth for that communication port. Thus, when the communication portP1 receives a data frame, it sends the data corresponding to that dataframe to the reception queue Fr1 by the link 25. The traffic regulator28 retrieves the data by reading them from the reception queue Fr1, forexample according to a FIFO principle, and it sends them to theprocessing unit 16. This example embodiment is particularly advantageouswhen the communication network is of the full-duplex Ethernet type, andthe communication port P1 is connected, by a link 14, to a communicationport of a subscriber of the communication network. The authorizedmaximum bandwidth for the communication port P1 is chosen to be equal tothe authorized maximum bandwidth for transmission on the network,associated with that subscriber. It is not therefore necessary toconfigure that authorized maximum bandwidth in the subscriber, thesubscriber thus being able to be provided with a standard Ethernetcommunication port. This example embodiment is duplicated in each one ofthe communication nodes 10 a, 10 b, . . . 10 i of the network, having acommunication port connected to a subscriber 12 a, 12 b, . . . 12 l.During the design or evolution of the network, it is appropriate todefine an authorized maximum bandwidth for transmission on the networkfor each of the subscribers and then to configure the communicationnodes connected to these subscribers with the bandwidths defined to beused by their traffic regulators. Although this example embodiment isparticularly advantageous in the case of a full-duplex Ethernet network,it can also be used in the abovementioned case of a communicationnetwork using a communication protocol compatible with the ARINC 664part 7 standard. It thus makes it possible to guarantee that, in thecase of a malfunction of a subscriber which would cause an exceeding ofthe authorized maximum bandwidth for that subscriber, the communicationnode would then limit the data traffic coming from said subscriber andretransmitted on the communication network.

Advantageously, the communication node 10 is integrated in a subscriber32 of the communication network, as shown in FIG. 6. Thus, in additionto the communication node 10, this subscriber 32 comprises a processingunit 12 p and a communication interface unit 12 n. The communicationnode 10 is connected to the communication interface unit by its port P1.The processing unit 12 p corresponds for example to an avionic computerof the aircraft and the communication interface 12 n corresponds forexample to a communication port of said computer. The communicationinterface unit 12 n and the communication port P1 can also correspond tocommunication software layers of said computer and of the communicationnode, which makes it possible for example to avoid the setting up ofphysical data transport layers between the computer and thecommunication node.

The integration of the communication node 10 in the subscriber 32 makesit possible to simplify the communication network, such that thecommunication network does not need specific equipment for implementingthe functions of a communication node. As shown in FIG. 7, thecommunication network thus comprises only subscribers 32 a, 32 b, . . .32 h and a set of links 14 between these subscribers. This allows savingspace and weight, which is particularly advantageous in the case of acommunication network of an aircraft.

While at least one exemplary embodiment of the present invention hasbeen shown and described, it should be understood that modifications,substitutions and alternatives may be apparent to one of ordinary skillin the art and can be made without departing from the scope of theinvention described herein. This application is intended to cover anyadaptations or variations of the specific embodiments discussed herein.In addition, in this application, the terms “comprise” or “comprising”do not exclude other elements or steps, the terms “a” or “one” do notexclude a plural number and the term “or” means either or both.Furthermore, characteristics or steps which have been described withreference to one of the above exemplary embodiments may also be used incombination with other characteristics or steps of other exemplaryembodiments described above.

What is claimed is:
 1. A communication network comprising: a set oflinks each supporting a specified bandwidth; a set of subscribers; atleast one communication node comprising a set of communication ports,these communication ports being connected to links of the set of links,wherein: each one of the set of subscribers is associated with anauthorized maximum bandwidth for transmission on the network, in such away that a sum of authorized maximum bandwidths corresponding torespective subscriber is less than or equal to said authorized maximumbandwidth associated with respective subscriber, said at least onecommunication node comprises a processing unit and a memory and theprocessing unit is configured for, when a data frame is received on oneof the communication ports of the communication node: checking if thememory contains an identifier associated with the data frame; and if thememory does not contain the identifier associated with the data frame:sending that data frame to all of the other communication ports of thecommunication node and storing the identifier associated with the dataframe in the memory.
 2. The communication network as claimed in claim 1,wherein links of the set of links are arranged in pairs in order to forma network of a full-duplex type.
 3. The communication network as claimedin claim 1, wherein subscribers of the set of subscribers are configuredfor communicating on the network according to a communication protocolcompatible with the ARINC 664 part 7 standard.
 4. The communicationnetwork as claimed in claim 3, wherein the identifier associated withthe data frame corresponds to a virtual link identifier and a sequencenumber of the frame.
 5. The communication network as claimed in claim 1,wherein subscribers of the set of subscribers are configured forcommunicating on the network according to a communication protocolcompatible with the Ethernet standard.
 6. The communication network asclaimed in claim 5, wherein the identifier associated with the dataframe corresponds to an identifier of a corresponding transmittingsubscriber and of a frame number generated by that subscriber.
 7. Thecommunication network as claimed in claim 1, comprising at least fourcommunication nodes each comprising four communication ports, thesecommunication nodes being arranged according to a matrix topology. 8.The communication network as claimed in claim 1, wherein said at leastone communication node is integrated in one of the set of subscribers.9. A communication node of a communication network, the communicationnetwork comprising: a set of links each supporting a specifiedbandwidth, and a set of subscribers, each one of the set of subscribersbeing associated with an authorized maximum bandwidth for transmissionon the network, in such a way that a sum of authorized maximumbandwidths corresponding to respective subscriber is less than or equalto the authorized maximum bandwidth associated with respectivesubscriber, the communication node comprising a set of communicationports, these communication ports being connected to links of thenetwork, wherein the communication node comprises a processing unit anda memory and the processing unit is configured for, when receiving adata frame on one of the communication ports of the communication node:checking if the memory contains an identifier associated with the dataframe; if the memory does not contain the identifier associated with thedata frame: sending that data frame to all of the other communicationports of the communication node; and storing, in the memory, theidentifier associated with the data frame.
 10. The communication node asclaimed in claim 9, further comprising a transmission queue associatedwith a communication port.
 11. The communication node as claimed inclaim 9, further comprising: a reception queue associated with acommunication port; and a traffic regulator associated with thecommunication port, the traffic regulator being configured for readingdata in the reception queue and for sending these data to the processingunit, whilst limiting the reading and sending of the data in terms of anauthorized maximum bandwidth for the communication port.
 12. Anaircraft, comprising a communication network as claimed in claim
 1. 13.A communication network on board a vehicle, the communication networkcomprising: a plurality of communication links; a plurality ofcommunication nodes; and a plurality of subscribers, each subscriberbeing connected to at least one of the plurality of communication nodes,and each subscriber being associated with an authorized maximumbandwidth for transmission on the communication network, such that a sumof authorized maximum bandwidths corresponding to respect subscriber isless than or equal to the authorized maximum bandwidth associated withrespective subscriber, wherein each communication node includes aplurality of communication ports and is configured to: when a data frameis received on one communication port of respective communication node,check whether the data frame has been transmitted by respectivecommunication node; and in response to the determination that the dataframe has not been transmitted by respective communication node, sendthe data frame to all the other communication ports of respectivecommunication node.
 14. The communication network according to claim 13,wherein at least one of the plurality of communication nodes isintegrated in one of the plurality of subscribers.
 15. The communicationnetwork according to claim 13, wherein each communication node furtherincludes a memory, and each communication node is further configured tostore an identifier of a data frame in its memory after the data framehas been transmitted by respective communication node.
 16. Thecommunication network according to claim 15, wherein each communicationnode is further configured to check whether its memory contains anidentifier of a data frame in determining whether the data frame hasbeen transmitted by respective communication node.
 17. The communicationnetwork according to claim 13, wherein each communication node furtherincludes: a reception queue and a traffic regulator associated with acommunication port of respective communication node, the trafficregulator being configured to limit reading and sending of data in thereception queue in terms of an authorized maximum bandwidth of thecommunication port.
 18. A communication node of a communication networkon board a vehicle, the communication network comprising: a plurality ofcommunication links; a plurality of communication nodes; and a pluralityof subscribers, each subscriber being connected to at least one of theplurality of communication nodes, and each subscriber being associatedwith an authorized maximum bandwidth for transmission on thecommunication network, such that a sum of authorized maximum bandwidthscorresponding to respect subscriber is less than or equal to theauthorized maximum bandwidth associated with respective subscriber,wherein each communication node includes a plurality of communicationports and is configured to: when a data frame is received on onecommunication port of respective communication node, check whether thedata frame has been transmitted by respective communication node; and inresponse to the determination that the data frame has not beentransmitted by respective communication node, send the data frame to allthe other communication ports of respective communication node.
 19. Thecommunication node according to claim 18, further comprising: areception queue and a traffic regulator associated with a communicationport of the communication node, the traffic regulator being configuredto limit reading and sending of data in the reception queue in terms ofan authorized maximum bandwidth of the communication port.
 20. Asubscriber of a communication network on board a vehicle, thecommunication network comprising: a plurality of communication links;and a plurality of communication nodes, the subscriber of thecommunication network being connected to the at least one of theplurality of communication nodes, and the subscriber being associatedwith an authorized maximum bandwidth for transmission on thecommunication network, such that a sum of authorized maximum bandwidthscorresponding to the subscriber is less than or equal to the authorizedmaximum bandwidth associated with the subscriber, wherein eachcommunication node includes a plurality of communication ports and isconfigured to: when a data frame is received on one communication portof respective communication node, check whether the data frame has beentransmitted by respective communication node; and in response to thedetermination that the data frame has not been transmitted by respectivecommunication node, send the data frame to all the other communicationports of respective communication node.